Electromagnetic contactor



Nov. 8, 1966 PETTIT ETAL 3,284,742

ELECTROMAGNETI C CONTACTOR Filed Aug. 17, 1964 2 Sheets-Sheet l .2 ilPeZif 5 5 jaz wjizip/ Nov. 8, 1966 D. L. PETTIT ETAL ELECTROMAGNETIC CONTACTOR Filed Aug. 17, 1964 2 Sheets-Sheet 2 [@5 6 limil! United States Patent 3,284,742 ELECTROMAGNETIC CONTACTOR Dorn L. Pettit and Edward J. Stark,'Milwaukee, W1s.,

assignors to Square D Company, Park Ridge, 111., a

corporation of Michigan Filed Aug. 17, 1964, Ser. No. 389,889 15 Claims. (Cl. 335193) This invention relates to an improved direct-current electromagnetic contactor which is extremely compact and low in cost relative to its current carrying ability and is thus suitable for use on industrial electric trucks, electrically-powered golf carts, and the like. The small size of the improved contactor permits it to replace the automotive type contactors, sometimes referred to as canned contactors, heretofore used for such applications, and to provide many advantages thereover.

The improved contactor has both front and back (i.e., both norm-ally open and normally closed) contacts and has its movable contacts at the free end of a cantilever. The resulting displacement of the path of movement of the contacts from the axis of a reciprocable actuating rod causes frictional engagement of the rod with its guide bearings thereby to reduce contact bounce of both the normally open and the normally closed contacts.

Bus bars or terminal straps carrying the stationary contacts of the improved contactor and a bus bar or terminal strap to which a flexible lead is attached are arranged with respect to the mounting surfaces of the contact-or so that electrical connections to the contactors are easily made when two or more of the contactors are connected in a reversing and accelerating circuit for a direct-current series motor.

Another feature of the invention is that any arcing at the contacts upon separation thereof occurs at selected areas as a result of a blow-out effect in a direction away from insulating supports. The blow-out effect results from current paths through the bus and contact structure of the contactor.

FIG. 1 is a front elevational view of a contactor constr-ucted in accordance with the invention;

FIG. 2 is a side elevational view of the contactor of FIG. 1;

FIG. 3 is a top plan view of the contactor of FIG. 1;

FIG. 4 is a sectional view taken substantially along the line 4-4 of FIG. 1;

FIG. 5 is a fragmentary view similar to the upper portion of FIG. 1, but showing the movable contacts shifted to a position corresponding with the energized condition of the coil of the contactor;

FIG. 6 is a top plan view of an assembly of three contactors similar to the contactor of FIGS. 1-5;

FIG. 7 is a front elevational view of the assembly of FIG. 6, with a portion broken away;

FIG. 8 is a side elevational view of the assembly of FIGS. 6 and 7; and

FIG. 9 is a circuit diagram for which the contactor assembly of FIGS. 6 and 7 is particularly adapted in the control of an electric truck or other electric battery powered vehicle.

FIGS. 1-5 disclose a contactor 20 constructed in accordance with the invention. The contactor 20' is provided with a magnet frame including a first generally L-shaped bracket 22 and a second generally L-shaped bracket 24, a leg portion 22a of the bracket 22 serving as a back plate and having a leg portion 24a of the bracket 24 secured thereto as by a pair of screws 25 provided with lock washers 26. A leg portion 22b of the bracket 22 serves as a top plate and is spaced from a leg portion 24b of the bracket 24 serving as a bottom plate to define a space which receives a coil 28 Wound on a spool 29 and having a pair of terminals 30. The bracket 22 is provided with an offset extension 220 adjacent the end of the leg portion 22a opposite the leg portion 22b, a pair of mounting holes 32 being provided in the extension 220. Welded or otherwise secured adjacent the end of the leg port-ion 22a opposite the extension 220 is a mounting plate 34 provided with a keyhole-shaped mounting aperture 35.

A stepped terminal and stationary contact support block 38 formed of insulating material is secured to the upper surface of the leg portion 22b by a pair of screws 39 and 40, the screws 39 being threaded into the leg portion 22b and the screw 40 being threaded into a tongue extension 22d extending from the leg portion 22b and recessed within the contact support block. The leg portion 22b is apertured to receive a reduced diameter end portion 42a of a generally cylindrical stationary magnetic core 42 which is welded or otherwise secured to the leg portion 22b on the opposite side thereof from the contact support block 38 and is received in a central aperture of the spool 29 adjacent one end thereof. An annular spring member 44 is disposed on the reduced diameter end portion 42a of the core 42 between the leg portion 22b and an upper flange 29a of the spool 29 to bias the spool 29 and the coil 28 thereon firmly against the leg portion 24b and prevent axial movement thereof relatively thereto. The core 42 is centrally apertured to receive an operating rod 45 mounted for reciprocal movement in a bushing 46 staked in the core at the reduced diameter end portion 42a.

The leg portion 24b is apertured to receive an annular portion 29b depending from a lower flange 290 of the spool 29, which is thus held in assembled relationship with the brackets 22 and 24 respectively by the core 42 and the annular depending port-ion 2%. Further, to prevent the spool 29 and the coil 28 thereon from rotating with respect to the brackets and thus maintain the terminals 30 in proper position, the leg portion 24b is also apertured to receive a boss 29d depending from the flange 290 of the spool.

A generally cylindrical armature 47 is resiliently mounted on a lower end portion of the operating rod 45 for limited reciprocal movement relatively thereto and is also loosely guided for reciprocal movement in the spool 29. In order to improve the flux pattern in the magnetic circuit when the coil 28 is energized to cause the armature 47 to be attracted toward the core 42, the core 42 is c-onically recessed at its lower end as indicated at 42b and the armature 47 is provided at its upper end with a conical portion 47a complementary to and receivable in the recess 42b. The armature 47 is biased away from the core 42 by a return spring 48 encircling the operating rod 45, seated at one end on the core within the recess 42b, and seated at the other end on the armature within an enlarged inner diameter portion provided in the conical portion 47a. The spring 48 is also a contact pressure spring for a pair of normally closed contacts hereinafter described. The armature is provided at its lower end with an enlarged inner diameter portion for receiving a plurality of washers 50, an O-ring 51 formed of rubber or other elastic material, a collar 52, a contact pressure spring 54 for a pair of normally open contacts hereinafter described, and an annular bushing 56 staked or otherwise secured in place in the lower end of the armature and serving both as a seat for the spring 54 and a bushing for the operating rod 45. The collar 52 is secured against movement axially of the operating rod and may be in the form of a snap ring snapped into a groove 45a in the operating rod. The O-ring 51 serves as a shock-absorber when the coil 28 is deenergized, as

-hereinafter explained.

extreme upper end portion of the operating rod 45 is threaded to receive a nut 64 which holds a washer 65, a lock washer 66, the insulator 58, the contact arm 57, the insulator 60, and the washer 62 in position on the rod 45. The lower end of the operating rod is slotted to receive a screwdriver while the nut 64 is tightened. Adjacent one end and on opposite sides, the movable contact arm is provided with a pair of movable contacts 68 and 70 brazed or otherwise secured thereto.

The stepped terminal and stationary contact support block 38 supports three bus bars or terminal straps 72, 73, and 74, the terminal strap 72 being secured adjacent one end to an upper rear portion or step of the block 38 and extending forwardly to dispose the free other end portion thereof over the opposite end portion of the movable ,contact arm 57 from the contacts 68 and 70, the terminal strap 73 being secured adjacent one end to the upper rear portion or step of the block 38 and extending forwardly in parallel, spaced and coplanar relationship with the terminal strap 72 to dispose the free other end portion thereof over the movable contact 68, and the terminal strap 74 being secured adjacent one end to a lower front portion or step of the block 38 and extending rearwardly in parallel, spaced, and non-coplanar relationship with the terminal straps 72 and.73 to dispose the free other end portion thereof under the movable contact 7 0.

A braided wire cable 76 is provided to electrically connect the terminal strap 72 and the contact arm 57, opposite end portions of the cable being brazed or otherwise secured respectively to the lower surface of the free end portion of the terminal strap 72 and the lower surface of the end portion of the contact arm opposite the contact 70. A stationary contact 77 is brazed or otherwise secured to the lower surface of the free end portion of the terminal strap 73 in normally open contact relationship with the movable contact 68. The contacts 68 and 77 thus form the pair of normally open contacts having the contact pressure spring 54. A stationary contact 78 is brazed or otherwise secured to the upper surface of the free end portion of the terminal strap 74 in normally closed relationship with the movable contact 70. The contacts 70 and 78 thus form the pair of normally closed contacts having the contact pressure spring 48. The terminal straps are respectively secured in place on the block 38- by three bolts 80 provided respectively with lock washers 81 and threaded into metal inserts (not shown) in the block 38.

When the coil 28 is energized, the armature 47 is attracted upwardly into engagement with the core 42, moving as a unit with the operating rod during the first portion of its upward stroke and moving relatively to the operating rod during the latter portion of its upward stroke to compress the spring 54 after the connect 68 has engaged the contact 77 and thus establish pressure between the contacts 68 and 77. When the coil 28 is deenergized, the spring 54 expands and pushes the bushing 56 and armature 47 downwardly relatively to the operating rod 45, and the pring 48 expands to move the armature 47 and operating rod 45 downwardly to engage the contact 70 with the contact 78 and establish pressure therebetween, the O-ring 51 acting as a shock absorber.

In the deenergized condition of the coil 28, the spring 48 acts through the armature 47 and collar 52 to exert a downward force resultant on the operating rod 45 collinear with the axis thereof, While an equal and opposite upward force resultant is exerted by the contact 78- on the contact 70 at a point spaced from the axis of the operating rod. The couple thus formed has a counterclockwise (FIG. 1) moment effect on the operating rod 45, contact arm 57, and armature 47 considered as a unit and increases the friction between the operating rod 45 and bushing 46 and between the armature 47 and spool 29 to reduce contact bounce upon deenergization of the coil 28.

In the energized condition of the coil 28, the spring 54 acts through the collar 52 to exert an upwardforce resultant on the operating rod 45 collinear with the axis thereof, while an equal and opposite downward force resultant is exerted by the contact 77 on the contact 68 at a point spaced from the axis of the operating rod. The couple thus formed has a clockwise (FIG. 5) moment effect on the operating rod 45 and contact arm 57 considered as a unit and increases the friction between the operating rod 45 and bushing 46 and between the operating rod 45 and bushing 56 to reduce contact bounce upon energization of the coil 28.

The positional and directional terms such as upper, front, downwardly, etc., as used herein are purely relative, it being possible to mount the contactor in various positions.

In the contactor 20 shown in FIGS. 1-5, the braided cable 76 and its associated terminal strap 72 are disposed toward the left end of the movable contact arm 57 in FIG. 1, while the movable contacts 68 and 70 and the associated stationary contacts 77 and 78 and terminal straps 73 and 74 are disposed toward the right end of the movable con tact arm 57 in FIG. 1. Other arrangements are possible, and an assembly of contactors with varying arrangements of cables,contacts, and terminal straps is shown in FIGS. 6 and 7, the assembly of contactors being particularly adapted for use in a reversing and accelerating control circuit for a direct-current series motor and the arrangement of the cables, contacts, and terminal straps in the separate contactors and the arrangement of the contactors with each other being particularly adapted to permit easy connections to power source and motor terminals. The assembly of FIGS. 6 and 7 includes a contactor F identical to the contactor 20 of FIGS. 1-5, a contactor R the left end of the movable contact arm 57r, and a c0ntactor A identical to the contactor R except that the movable contact 70a, stationary contact 78a, and terminal strap 74a corresponding respectively to the movable contact 70r, stationary contact 78r, and terminal strap 74r have been omitted.

A bus bar 83 is provided to electrically connect the terminal strap 73 of the contactor F and the terminal strap 73r of the contactor R. A bus bar 8-4 is provided to electrically connect the terminal strap 74 of the contactor F and the terminal strap 74r of the contactor R. In addition, a solid wire conductor 85 is provided to electrically connect the bus bar 84 and the terminal strap 73a of the contactor A; The contactors F, R, and A are secured together by a tie bar 86 having a stiffening rib 86a and having appropriate apertures (not shown) for receiving the screws 25 which hold the brackets 22 and 24 of the respective contactors together.

The F, R, and A designations of the contactors indicate Forward, Reverse, and Accelerate in the control of a direct-current series motor. In FIGS. 6 and 7, the bolts 80 of the contactors have been distinguished respectively by letter additions s, t, u, v, w, x, y, and z. The bolts 80s, SW, 8014, 80v, 80w, 80x, 80y, and 801 serve as terminal connectors. As shown in the diagram of FIG. 9, the positive terminal of a battery b of an electric truck may be electrically connected to either of connectors or bolts SW and 8011, which are joined by the bus bar 83. A field winding 1 of a direct current series motor of an electric truck may be electrically connected at opposite ends respectively to the connectors 80s and SUV. An armature winding a of the direct-current series motor may be electrically connected at opposite ends respectively to the connector 80x and the negative terminal of the battery b. A resistor r may be electrically connected at one end to any of the connectors 80y, 802, and 80w, and at the other end to the connector 80x, the connectors 80y and 80z being joined by the bus bar 84 and the connectors 80z and 80w being joined by the conductor 85.

When neither the contactor F nor the contactor R is energized, there is no circuit completed through the battery, because the circuit is open at the normally open contacts 68]- and 77 of the contactor F and at the normally open contacts 68r and 77r of the contactor R. If the coil of the contactor F is then energized to cause the motor to rotate in the forward direction, the normally open contacts 68 and 77 are closed and the normally closed contacts 70 and 78 are opened. A circuit is then completed from the positive terminal of the battery b through the contacts 77 and 68 through the field winding 1'' in the direction from connector 80s to connector 80v, through the contacts 70r and 78r, the resistor r, and the armature Winding a to the negative terminal of the battery b. If, while the contactor F is energized, the coil of the contactor A isthen energized, the normally open contacts 68a and 7711 are closed to by-pass the resistor r and cause the motor to rotate faster in the forward direction.

If, instead of the coil of the contactor F, the coil of the contactor R is energized to cause the motor to rotate in the reverse direction, the normally open contacts 68r and 77r are closed and the normally closed contacts 701' and 78r are opened. A circuit is then completed from the positive terminal of the battery b through the contacts 77r and 681*, through the field winding 1 in the direction from connector 89v to connector 80s, through the contacts 70f and 78f, the resistor r, and the armature winding a to the negative terminal of the battery b. If, while the contactor R is energized, the coil of the contactor A is then energized, the normally open contacts 68a and 77a are closed to by-pass the resistor r and cause the motor to rotate faster in the reverse direction.

The current path through any of the contactors F, R, and A when the coil of the respective contactor is energized is such that upon deenergization of the coil and separation of the normally open contacts 68] and 77 68r and 77r, or 68a and 77a, any arcing that occurs is subject to a desirable blow-out eflect due to the tendency of the current loop to expand away from the insulators supporting the respective movable contact arm and away from the upper rear portion of the respective stationary contact block.

It will be seen that an improved contactor has been provided having a novel means of reducing contact bounce, and that a compact contactor assembly has been provided which affords easy connection of leads from a battery, a field winding, and an armature winding of a direct-current series motor.

Various modifications may be made in the structure shown and described without departing from the spirit and scope of the invention, as set forth in the claims appended hereto.

We claim:

1. An electromagnetic contactor comprising a magnet frame, an energizable coil magnetically associated with said magnet frame, an armature magnetically associated with said magnet frame and coil and reciprocable upon energization and deenergization of said coil, an operating rod having an end portion connected to said armature for reciprocation therewith, an elongated movable contact arm extending generally perpendicularly to and centrally supported by the other end portion of said operating rod, a bushing disposed between said armature and movable contact arm and reciprocally guiding said operating rod, a pair of terminal members respectively disposed adjacent opposite end portions of said movable contact arm, a flexible electrical conductor electrically connecting one of said terminal members and one end portion of said movable contact arm, said movable contact arm having a movable contact portion on the other end portion thereof, and the other of said terminal members having a stationary contact portion engageable by said movable contact portion of said movable contact arm upon energization of said coil, the reaction force of said stationary contact portion against said movable contact arm tending to tilt said operating rod and increasing friction between said operating rod and said bushing to reduce contact bounce upon energization of said coil.

2. An electromagnetic contactor comprising a magnet frame, an energizable coil magnetically associated with said magnet frame, an armature magnetically associated with said magnet frame and coil and reciprocable upon energization and deenergization of said coil, an operating rod having an end portion extending through said armature for reciprocal movement relatively thereto, a first bushing disposed in said armature and reciprocally guiding said operating rod, an elongated movable contact arm extending generally perpendicularly to and centrally supported by the other end portion of said operating rod, a spring in said armature biasing said armature with respect to said operating rod in a direction away from said movable contact arm, a second bushing disposed between said .armature and movable contact arm and reciprocally guiding said operating rod, a pair of terminal members respectively disposed adjacent opposite end portions of said movable contact arm, a flexible electrical conductor electrically connecting one of said terminal members and one end portion of said movable contact arm, said movable contact arm having a movable contact portion on the other end portion thereof, and the other of said terminal members having a stationary contact portion engageable by said movable contact portion of said movable contact arm upon energization of said coil, the reaction force of said stationary contact portion against said movable contact arm tending to tilt said operating rod and increasing friction between said operating rod and said first and second bushings to reduce contact bounce upon energization of said coil.

3. An electromagnetic contactor comprising a magnet frame, an energizable coil magnetically associated with said magnet frame, an armature magnetically associated with said magnet frame and coil and reciprocable upon energization and deenergization of said coil, said armature having a portion reciprocally guided by said coil, an operating rod having an end portion connected to said armature for reciprocation therewith, an elongated movable contact arm extending generally perpendicularly to and centrally supported by the other end portion of said operating rod, a bushing disposed between said armature and movable contact arm and reciprocally guiding said operating rod, a first terminal member disposed adjacent an end portion of said movable contact arm, a flexible electrical conductor electrically connecting said first terminal member and said end portion of said movable contact arm, a second terminal member and a third terminal member disposed adjacent the other end portion of said movable contact arm on opposite sides thereof, said other end portion of said movable contact arm having a pair of movable contact portions respectively on opposite sides thereof, said second terminal 7. member having a stationary contact portion engageable by one of said movable contact portions of said movable contact arm upon energization of said coil, and said third terminal member having a stationary contact portion engageable by the other of said movable contact portions of said movable contact arm upon deenergization of said coil, the reaction force of said stationary contact portion of said third terminal member against said movable contact arm tending to tilt said operating rod and armature and increasing friction between said operating rod and said bushing and between said armature and said coil to reduce contact bounce upon deenergization of said coil.

4. An electromagnetic contactor comprising a magnet frame, an energizable coil magnetically associated with said magnet frame, an armature magnetically associated with said magnet frame and coil and reciprocable upon energization and deenergization of said coil, said arma ture having a portion reciprocally'guided by said coil, an operating rod having an end portion extending through said armature for reciprocal movement relatively thereto, a first bushing disposed in said armature and reciprocally guiding said operating rod, an elongated movable contact arm extending generally perpendicularly to and centrally supported by the other end portion of said operating rod, a spring in said armature biasing said armature with respect to said operating rod in a direction away from said movable contact arm, a second bushing disposed between said armature and movable contact arm and reciprocally guiding said operating rod, a first terminal member disposed adjacent an end portion of said movable contact arm, a flexible electrical conductor electrically connecting said first terminal member and said end portion of said movable contact arm, a second terminal member and a third terminal member disposed adjacent the other end portion of said movable contact arm on opposite sides thereof, said other end portion of said movable contact arm having a pair of movable contact portions respectively on opposite sides thereof, said second terminal member having a stationary cotnact portion engageable by one of said movable contact portions of said movable contact arm upon energization of said coil, and said third terminal member having a stationary contact portion engageable by the other of said movable contact portions of said movable contact arm upon deenergization of said coil, the reaction force of said stationary contact portion of said second terminal member against said movable contact arm tending to tilt said operating rod in one direction and increasing friction between said operating rod and said first and second bushings to reduce contact bounce upon energization of said coil, and the reaction force of said stationary contact portion of said third terminal member against said movable contact arm tending to tilt said operating rod and armature in the other direction and increasing friction between said operating rod and said second bushing and between said armature and said coil to reduce contact bounce upon deenergization of said coil.

5. An electromagnetic contactor comprising a stepped terminal and stationary contact block formed of insulating material and having upper and lower step portions, a pair of spaced terminal straps respectively mounted on said upper step portion adjacent opposite ends thereof and having end portions extending over said lower step portion in spaced relationship thereto, a reciprocably mounted operating rod extending through said lower step portion between said terminal straps, an elongated generally flat movable contact arm centrally supported by said operating rod in insulated relationship thereto and disposed between said end portions of said terminal straps and said lower step portion, a flexible electrical conductor electrically connecting said end portion of one of said terminal straps and one end portion of said movable contact arm, a movable contact on the other end portion of said movable contact arm on the side thereof facing the other of said terminal straps, energizable and deenergizable electromagnetic means for reciprocably moving said terminal straps and one end portion of said movable portion of said other terminal strap engageable by said movable contact upon energization of said electromagnetic means.

6. An electromagnetic contactor as claimed in claim 5, including a third terminal strap mounted on said lower step portion and having an end portion adjacent said other end portion of said movable contact arm, a second movable contact on said other end portion of said movable contact arm on the side thereof facing said third terminal strap, and a stationary contact on said end portion of said third terminal strap engageable by said second movable contact upon deenergization of said electromagnetic means.

7. An electromagnetic contactor comprising a generally U-shaped magnet frame, an energizable coil supported within said magnet frame between a pair of leg portions thereof, a stationary core in said coil adjacent one end thereof, a movable armature in said coil adjacent the other end thereof and adapted to be attracted toward said core upon energization of. said coil, a stepped terminal and stationary contact block formed of insulating material and supported on the one of said leg portions adjacent said core on the other side of said one leg portion from said coil, an operating rod connected to said armature and extending through said core, magnet frame, and block, an elongated generally flat movable contact arm supported centrally thereof on and in insulated relationship to an end portion of said operating rod extending outwardly of said block, a spring between said core and armature biasing said armature, operating rod, and movable contact arm in a direction tending to move said movable contact arm toward said block, a movable contact mounted on one end portion of said movable contact arm on the opposite side thereof from said coil, a first terminal strap having one end portion mounted on a step of said block remote from said coil and extending in spaced relationship to a step of said block adjacent said coil and having its other end portion disposed in overlapping spaced relationship to said movable contact, a stationary contact mounted on said other end portion of said first terminal strap on the side thereof facing said coil and adapted to be engaged by said movable contact upon energization of said coil, a second terminal strap having one end portion mounted on said step of said block remote from said coil and extending in spaced relationship to said step of said block adjacent said coil and having its other end portion disposed in overlapping spaced relationship to the other end portion of said movable contact arm, and a flexible electrical conductor electrically connecting said other end portion of said second terminal strap and said other end portion of said movable contact arm.

8. An electromagnetic contactor as claimed in claim 7, including a second movable contact mounted on said one end portion of said movable contact arm on the side thereof facing said coil, a third terminal strap having one end portion mounted on said step of said block adjacent said coil and extending therealong and having its other end portion disposed in overlapping spaced relationship to said second movable contact, and a stationary contact mounted on said other end portion of said third terminal strap on the opposite side thereof from said coil and adapted to be engaged by said second movable contact when said coil is deenergized.

9. An electromagnetic contactor as claimed in claim 7, wherein said armature is reciprocably mounted on said operating rod and a spring is provided in said armature, said spring biasing said armature toward the end of said operating rod opposite said movable contact arm.

10. An electromagnetic contactor as claimed in claim 8, wherein said armature is reciprocably mounted on said operating rod and a spring is provided in said armature.

9 said spring biasing said armature toward the end of said operating rod opposite said movable contact arm.

11. An assembly of electromagnetic contactors particularly adapted to control the operation of a direct-current motor having a field winding in series with an armature winding, said assembly comprising first and second electromagnetic contactors mounted side by side, each of said contactors including a stepped terminal and stationary contact block formed of insulating material and having upper and lower step portions, a pair of spaced terminal straps respectively mounted on said upper step portion adjacent opposite ends thereof and having ends portions extending over said lower step portion in spaced relationship thereto, a reciprocably mounted operating rod extending through said lower step portion between said terminal straps, an elongated generally fiat movable contact arm centrally supported by said operating rod in insulated relationship thereto and disposed between said end portions of said terminal straps and said lower step portion, and energizable and deenergizable electromagnetic means for reciprocably moving said operating rod, said first contactor including a flexible electrical conductor electrically connecting the terminal strap on the respective upper step portion and remote from said second contactor and the end portion of the respective movable contact arm remote from said second contactor, a pair of movable contacts on the end portion of the respective movable contact arm adjacent said second contactor and respectively disposed on opposite sides of the respective movable contact arm, a stationary contact disposed on the other terminal strap on the respective upper step portion adjacent said second contactor and engageable by one of the respective movable contacts upon energization of the respective electromagnetic means, a terminal strap mounted on the respective lower step portion adjacent the end thereof adjacent said second contactor, and a stationary contact disposed on the terminal strap on the respective lower step portion and engageable by the other of the respective movable contacts upon deenergization of the respective electromagnetic means, said second contactor including a flexible electrical conductor electrically connecting the terminal strap on the respective upper step portion and remote from said first contactor and the end portion of the respective movable contact arm remote from said first contactor, a pair of movable contacts on the end portion of the respective movable contact arm adjacent said first contactor and respectively disposed on opposite sides of the respective movable contact arm, a stationary contact disposed on the terminal strap on the respective upper step portion adjacent said first contactor and engageable by one of the respective movable contacts upon energization of the respective electromagnetic means, a terminal strap mounted on the respective lower step portion adjacent the end thereof adjacent said first contactor, and a stationary contact disposed on the terminal strap on the respective lower step portion and engageable by the other of the respective movable contacts upon deenergization of the respective electromagnetic means, a first electrical conductor electrically connecting the terminal strap on the upper step portion of said first contactor adjacent said second contactor and the terminal strap on the upper step portion of said second contactor adjacent said first contactor, and a second electrical conductor electrically connecting the terminal strap on the lower step portion of said first contactor and the terminal strap on the lower step portion of said second contactor.

12. An assembly as claimed in claim 11, wherein said first and second electrical conductors are generally flat bus bars.

13. An assembly of electromagnetic contactors particularly adapted to control the operation of a direct-current motor having a field winding in series with an armature winding, said assembly comprising first, second, and third electromagnetic contactors mounted side by side in 10 a row, each of said contactors including a stepped terminal and stationary contact block formed of insulating material and having upper and lower step portions, a pair of spaced terminal straps respectively mounted on said upper step portion adjacent opposite ends thereof and having end portions extending over said lower step portion in spaced relationship thereto, a reciprocably mounted operating rod extending through said lower step portion between said terminal straps, an elongated generally flat movable contact arm centrally supported by said operating rod in insulated relationship thereto and disposed between said end portions of said terminal straps and said lower step portion, and ener gizable and deenergizable electromagnetic means for reciprocably moving said operating rod, said first contact-or being disposed adjacent said second contactor and including a flexible electrical conductor electrically connecting the terminal strap on the respective upper step portion and remote from said second contactor and the end portion of the respective movable contact arm remote from said second contactor, a pair of movable contacts on the end portion of the respective movable contact arm adjacent said second contactor and respectively disposed on opposite sides of the respective movable contact arm, a stationary contact disposed on the other terminal strap on the respective upper step portion adjacent said second contact-or and engageable by one of the respective movable contacts upon energization of the respective electromagnetic means, a terminal strap mounted on the respective lower step portion adjacent the end thereof adjacent said second contactor, and a stationary contact disposed on the terminal strap on the respective lower step portion and engageable by the other of the respective movable contacts upon deenergization of the respective electromagnetic means, said second contactor including a flexible electrical conductor electrically connecting the terminal strap on the respective upper step portion and remote from said first contactor and the end portion of the respective movable contact arm remote from said first contactor, a pair of movable contacts on the end portion of the respective movable contact arm adjacent said first contactor and respectively disposed on opposite sides of the respective movable contact arm, a stationary contact disposed on the terminal strap on the respective upper step portion adjacent said first contactor and engageable by one of the respective movable contacts upon energization of the respective electromagnetic means, a terminal strap mounted on the respective lower step portion adjacent the end thereof adjacent said first contactor, and a stationary contact disposed on the terminal strap on the respective lower step portion and engageable by the other of the respective movable contacts upon deenergization of the respective electromagnetic means, said third contactor being disposed adjacent one of said first and second contactors and including a flexible electrical conductor electrically connecting one of the terminal straps on the respective upper step portion and one of the end portions of the respective movable contact arm, a movable contact on the other end portion of the respective movable contact arm and disposed on the side of the respective movable contact arm facing the other of the terminal straps on the respective upper step portion, and a stationary contact disposed on said other terminal strap on the respective upper step portion and enga-geable by the respective movable contact upon energization of the respective electromagnetic means, a first electrical conduct-or electrically connecting the terminal strap on the upper step portion of said first contactor adjacent said second contactor and the terminal strap on the upper step portion of said second contactor adjacent said first contactor, a second electrical conductor electrically connecting the terminal strap on the lower step portion of said first contactor and the terminal strap on the lower step portion of said second contactor, and a third electrical conductor electrically connecting 1 1 said second electrical conductor and said other terminal strap of said third oontactor.

14. An assembly as claimed in claim 13, wherein said first and second electrical conductors are generally flat bus bars.

15. An assembly as claimed in claim 13, wherein the end portion of said movable contact arm of said third conta-ctor having said movable contact mounted thereon is disposed adjacentsaid one of said first and second 0ontactors and the end portion of said movable contact arm of said third contactor having said flexible electrical conductor connected thereto is disposed remote from said one of said first and second contactors.

References Cited by the Examiner UNITED STATES PATENTS 736,476 8/1903 Baxter 200-98 5 2,919,324 12/1959 Schuessler 200104 3,076,075 1/1963 Colvill 200104 FOREIGN PATENTS 541,652 4/1956 Italy.

10 BERNARD A. GILHEANY, Primary Examiner.

J. I. BAKER, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,284,742 November 8, 1966 Born L. Pettit et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 17, for "screws" read screw column 3, line 70, for "connect" read contact column 4, line 55, for "and and" read and column 7, line 39, for "cotnact" read contact column 8, line 2, strike out "terminal straps and one end portion of said movable" and insert instead operating rod, and a stationary contact on said end column 9 line 12 for "ends" read end Signed and sealed this 12th day of September 1967.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. AN ELECTROMAGNETIC CONTACTOR COMPRISING A MAGNET FRAME, AN ENERGIZABLE COIL MAGNETICALLY ASSOCIATED WITH SAID MAGNET FRAME, AN ARMATURE MAGNETICALLY ASSOCIATED WITH SAID MAGNET FRAME AND COIL AND RECIPROCABLE UPON ENERGIZATION AND DEENERGIZATION OF SAID COIL, AN OPERATING ROD HAVING AN END PORTION CONNECTED TO SAID ARMATURE FOR RECIPROCATION THEREWITH, AN ELONGATED MOVABLE CONTACT ARM EXTENDING GENERALLY PERPENDICULARLY TO AND CENTRALLY SUPPORTED BY THE OTHER END PORTION OF SAID OPERATING ROD, A BUSHING DISPOSED BETWEEN SAID ARMATURE AND MOVABLE CONTACT ARM AND RECIPROCALLY GUIDING SAID OPERATING ROD, A PAIR OF TERMINAL MEMBERS RESPECTIVELY DISPOSED ADJACENT OPPOSITE END PORTIONS OF SAID MOVABLE CONTACT ARM, A FLEXIBLE ELECTRICAL CONDUCTOR ELECTRICALLY CONNECTING ONE OF SAID TERMINAL MEMBERS AND ONE END PORTION OF SAID MOVABLE CONTACT ARM, SAID MOVABLE CONTACT ARM HAVING A MOVABLE CONTACT PORTION ON THE OTHER END PORTION THEREOF, AND THE OTHER OF SAID TERMINAL MEMBERS HAVING A STATIONARY CONTACT PORTION ENGAGEABLE BY SAID MOVABLE CONTACT PORTION OF SAID MOVABLE CONTACT ARM UPON ENERGIZATION OF SAID COIL, THE REACTION FORCE OF SAID STATIONARY CONTACT PORTION AGAINST SAID MOVABLE CONTACT ARM TENDING TO TILT SAID OPERATING ROD AND INCREAING FRICTION BETWEEN SAID OPERATING ROD AND SAID BUSHING TO REDUCE CONTACT BOUNCE UPON ENERGIZATION OF SAID COIL. 